Charles francis jenkins



C. F. JENKINS.

ELECTRIC METER.

APPLXCATION FILED JUNE 22, 1918.

Patented Jan. 4, 192 1.

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meter without articulating parts, and one CHARLES FRANCIS JEN KINS, OF WASHINGTON, IDISllRIC'J. OF COLT JMBIA.

ELECTRIC mnrn'n.

Specification of Letters Patent.

Patented Jan. 4, 1921.

Application filedJune 22, 1918. Serial No. 241,886.

To all whom it may concern:

Be it known that I, CHARLES F RANOIS JENKINS, a citizen of the .United States, and resident of Washington, in the District of Columbia, have invented certain new and useful Improvements in Electric Meters, of which the following is 'a specification, reference being had-therein to the accompanying drawing.

This invention relates to indicating the heating effect of an electric current and thus approximately showing the strength of the current itself.

The principal objects are to provide an extremely inexpensive, simple and durable that will last indefinitely, even with rough use by careless or uninstructed users.

With these objects in view, an expansion bar, made in a well known way of two metals united face to face and differing in expansion when temperature rises, is longitudinally divided, except near one free end, and has the two parts or arms fixed, respectively, to the terminals of a circuit the current in which is to be measured, the deflection' of the bar indicating the current passing through it.

In the accompanying drawings, 7 Figure 1 is a face new of the thermostat. Fig. 2 is'a view looking'in the direction of the arrow of Fig. 1, the casing being in section.

Fig. 3 is a plan view of an expansion strip. Fig. 4 1s a crosssection of the same stri Fig. 5 is a lan view of the same strip after it is sawed longitudinally along its medial line. p r

In these figures, A represents a meter casing, B an insulating late fixed to the bottom of the casing, D binding posts secured to the plate B, extending outward through the bottom of the casing and nwardly from the plate, their free ends carrying, respectively, the ends E, E, of an expansion bar F, made up of metals having different coefficients of expansion, e. g. brass and steel. This bar is divided along its me' dial longitudinal axis to form parts or arms E, E in a plane and slightly separated except at one end where they are connected integrally by an uncut end portion of the bar. The bar thus divided is bent to the form shown in Fig. 1, forming two long don-- ble arms. J, K connected near the middle of the bar by a nearly complete loop L of cythrough the bottom of the casing, without 7 making electrical contact therewith, and re- .ceive, respectively the terminal 0, O of a circuit the current in which is to be indicated. The free end of the double arm K willobviously swing when the expansion bar as a whble is heated and this movement will be aided and increased in amplitude by the flexing of the arm J and the loop L, and thus a slight change in temperature will give a wide indicating movement of this free end of the arm K.

Preferably the casingPis provided with a protecting lass plate and between .this plate and tie expansion bar is an opaque disk Q having a graduated arc alongside a curved opening R throughwhich the free end of the arm K is visible and along which nor any ordinary use can impairthe usefulness of the meter.

What I claim is:

1. The combination with two parallel slightly separated arms connected at one end and having the opposite ends fixed and in electricalconnection with the terminals, respectively, of a circuit, the current m which is to be indicated, said arms havlng on opposite faces metals differing in expansion under increase in temperature, whereby the ends of the arms which are connected together pass from normal position through a distance commensurate with the heating and the current which heats.

2. A compensation bar divided from one end nearly to the opposite end and as a whole bent centrally to form aloop in the plane of the parts between which it lies, the separated ends being adapted for connection with the terminals of an electric circuit and fixed in position while the parts upon the opposite side of the loop are free to swing as a pointer when the heating eflect of the current varies.

3. In an electric ineter, a thermostatic two-metal strip bent near its middle to form an approximately cylindrical loop inthe plane of the other parts, the strip being split roIn one end nearly to the opposite end and the branches so formed having their free ends fixed and adapted to be electrically con nected, respectively, to the terminals of a circuit in which the current is to be measured, while the free end of the strip as a whole is free to swing as the heating efiect of the current varies. 7 

